First of all ,although CULA_BIN_PATH variable was defined and linked in the VS2005 according to the manual, I got "cula.dll was not found" error and I solved this issue by copying the .dll s to the project directory but I didn't understand why I got this error.

Then, I tried to run geqrf_device example, and I got runtime error (5) after "Calling culadeviceSgeqrf" message on the console. What should I do?

The BIN path is something of a problem in windows, because of how DLLs are located at runtime - basically search the PATH variable and the directory the executable resides in. The linker uses CULA_LIB_PATH to find the cula.lib file - this file mostly tells your exe to search for a cula.dll file at runtime. Your solution was correct though - CULA 2.1 is designed to work with CUDA 3.1. CUDA 3.2 support is coming soon.